1. Field of the Invention
The present invention relates to a method for manufacturing a flash memory, and more particularly, to a method for manufacturing a flash memory by using a spacer as an STI oxide spacer.
2. Description of the Prior Art
The flash memory is widely used because of its capability of non-volatile information storage. Generally speaking, the flash memory is divided into two groups, the NOR flash memory and the NAND flash memory.
In the production of the NAND flash memory, a shallow trench isolation (STI) is usually formed by a dry etching and later the location and the shape of the poly-Si of the floating gate are defined by the STI.
However, as shown in FIG. 1, the profile of the trench formed by the dry etching must be in a shape of an “inverted trapezoid” when the STI 120 is formed by dry etching the substrate 110 and filling with an isolation material. Accordingly, the chosen location of the floating gate 130 must be in the shape of a trapezoid and have poly-Si remained therein, which will affect the isolation as well as allocation of each individual floating gate, such as bits independence and distribution and cause confusion and error of data access, such as data storage shortage.
Therefore, a novel method is needed for manufacturing the flash memory, which is capable of amending the flawed profile of the STI oxide to solve the problem.